Acid fractional esters of oxypropylated hexanetriol-1, 2, 6



Fatentecl Sept. I5, 1953 OFFICE ACID FRACTIONAL ESTERS OF OXYPRO- PYLATED HEXANETRIOL-1,2,6

Melvin De Groote, University City, Mo., assignor to Petrolite Corporation, a corporation of Delaware No Drawing. Application May 14, 1951, Serial No. 226,329

9 Claims. (01. 260-475) The present invention is a continuation-inpart of my co-pending applications, Serial No. 104,801, filed July 14, 1949, now Patent No. 2,552,528, and Serial No. 159,863, filed May 3, 1950, now Patent No. 2,602,004.

The present invention is concerned with certain new chemical products, compounds, or compositions which have useful application in various arts. It includes methods or procedures for manufacturing said new chemical products, compounds or compositions, as well as the products, compounds, or compositions themselves.

Complementary to the above aspect of the invention herein disclosed is my companion invention concerned with the use of these particular chemical compounds, or products, as demulsifying agents in processes or procedures particularly adapted for preventing, breaking, or resolving emulsions of the water-in-oil type, and particularly petroleum emulsions. See my copending application, Serial No. 226,328, filed May 14, 1951, now Patent No. 2,626,911.

Aforementioned co-pending application, Serial No. 104,801, describes the resolution of petroleum emulsions by the oxypropylated derivatives of certain polyhydric materials free from a radical having at least 8 uninterrupted carbon atoms. Additionally said aforementioned co-pending application points out that certain derivatives, for instance, the esters derived from polycarboxy acids, can be employed for the same purpose, 1. e., process for breaking petroleum emulsions. My co-pending application, Serial No. 159,863 describes a process for breaking petroleum emulsions of the water-in-oil type characterized by subjecting the emulsion to the action or" a demulsiiier including a monomeric acidic fractional ester of the following structure:

o oiH60)"o0R' oooH),.'

R o o3H,o),,ooR' ooH)..'

)(C3HuO)1 OCB/(COOH),,

in which R is the radical of a water-soluble triol RUDE); whose elements consist of carbon, hydrogen oxygen only, and R is the polycarboxy acid radical of the conventional polycarboxy acid coon \(COOH),,, in which n represents the whole numbers 1 to 2, and n represents a whole number varying from 6 to 30; with the proviso that n be the statistical average based on the amount of propylene oxide reacted with the initial triol R(OH)3; said triol being free from any radical having at least 8 uninterrupted carbon atoms; and with the further proviso that the oxypropylated triol O (0 SE6 0 )"H 0 (Q3110 0),.H be water -insoluble and Xylene-soluble, and that the statistical average molecular weight of said oxypropylated triols be within the range of 1,000 to 5,000.

Briefly stated, the present invention is concerned with a monomeric acidic fractional ester of the following structure:

o 0311,, o ,,ooR' o 0 0H),, RO(CsHa0)n CR(COOH),.1

o (C3HaO),,OCR(C 0 0H),, in which R is the radical of heXanetriol-1,2,6, and R is the polycarboxy acid radical of the conventional polycarboxy acid COOH (ooorna in which n represents the whole numbers 1 to 2, and n represents a whole number varying from 6 to 30; with the proviso that n be the statistical average based on the amount of propylene oxide reacted with the initial triol R(OH)3; said triol being free from any radical having at l ast 8 uninterrupted carbon atoms; and with the further proviso that the oxypropylated triol o(o3Hio),,H

R-O(C3H@O),.H

O(CaEtO)nH be kerosene-soluble, and that the statistical average molecular weight of said oxypropylated triol-s be within the range of 1,000 to 10,000.

Although the herein described products have a number of industrial applications, they are of particular value for resolving petroleum emu1- sions of the water-in-oil type that are commonly referred to as cut oil, roily oil, emulsified oil, etc., and which comprise fine droplets of naturally-occurring waters or brines dispersed in a more or less permanent state throughout the oil which constitutes the continuous phase of the emulsion. This specific application is described and claimed in my co-pending application, Serial No. 226,328, filed May 14, 1951.

The new products are useful as wetting, deter.

gent and leveling agents in the laundry, textile and dyeing industries; as wetting agents and detergents in the acid washing of building stone and brick; as wetting agents and spreaders in the application of asphalt in road building and the like; as a flotation reagent inthe flotation separation of various aqueous suspensions containing negatively charged particles, such as sewage, coal washing waste water, and various trade wastes and the like; as germicides, insecticides, emulsifying agents, as, for example, for cameras, spray oils, water-repellent textile finishes; as lubricants, etc. 7

For convenience, what is said hereinafter will be divided into two parts:

Part 1 will be concerned with the preparation of oxypropylated derivatives of hexanetrioll,2,-6; and

Part 2 will be concerned with the preparation of acidic fractional esters by reacting the polyhydroxylated compounds withpolycarboxy acids.

PART 1 For a number of well known reasonsequipment, whether laboratory size, semi-pilot plant size, pilot plant size, or large scale size, is not as a rule designed for a particular alkylene oxide. Invariably and inevitably, however, or particularly in the case of laboratory equipment and pilot plant size the design is such as to use any of the customarily available alkylene oxides, i. e-., ethylene oxide, propylene oxide, butylene oxide, glycide, epichlorohydrin, styrene oxide, etc. In the subsequent description of the equipment it becomes obvious that it is adapted for oxyethylation as well as oxypropylation.

Oxypropylations are conducted under a wide variety of conditions, not only in regard to presence or absenc of catalyst, and the kind of catalyst, but also in regard to the'time of reaction, temperature of reaction, speed of reaction, pressure during reaction; etc. For instance, oxyalkylations can be conducted at temperatures up to approximately 200 C. with pressures in about the same range up to about 200 pounds per square inch. They can be conducted also at temperatures approximating the boiling point of water or slightly above, as for example 95 to 120 C. Under such cir'cumstances'the pressure will be less than 30 pounds per square inch unless some special procedure is employed as is sometimes the case, to wit, keeping an atmosphere of inert gas such as nitrogen in the vessel during the reaction. Such low temperature-low reaction rate oxypropylations have been described very completely in U.'S. Patent No. 2,448,664, to H. R. Fife, et al., dated September '7', 1948. Low temperature, low pressure oxypropylations are particularly desirable Where the compound being subjected to oxypropylation contains one, two or three points of reaction only, such as monohydric alcohols, glycols and triols.

Since low pressure-low temperature-low reaction speed oxypropylations require considerable time, for instance, 1 to '7 days of 24 hours each to complete the reaction they are conducted as a rul whether on'a laboratory scale, pilot plant scale, or large scale, so as to operate automatically. The prior figure of seven days applies especially to large-scale operations. I have used conventional equipment with two added automatic features; (a) a solenoid controlled valve which shuts off the propylene oxide in event that the temperature gets outside a predetermined and set range, for instance, 95 to 120 C., and

(b) another solenoid valve which shuts on? the propylene oxide (or for that matter ethylene oxide if it is being used) if the pressure gets beyond a predetermined range, such as 25 to 35 pounds. Otherwise, the equipment is substantially the same as is commonly employed for this purpose where the pressure of reaction is higher, speed of reaction is higher, and time of reaction is much shorter. In such instances such automatic controls are not necessarily used.

Thus, in preparing the various examples I have found it particularly advantageous to use laboratory equipment or pilot plant equipment which is designed to permit continuous oxyalkylation whether it be oxypropylation or oxyethylation. With certain obvious changes the equipment can be used also to permit oxyalkylation involving the use of glycide where no pressure is involved except the vapor pressure of a solvent, if any, which may have been used as a diluent.

As previously pointed out the method of'using propylene oxide is the same as ethylene oxide. This point is emphasized only for the'reason that the apparatus is so designed and constructed as to use either oxide.

The oxypropylation procedure employed in the preparation of the oxyalkylated derivatives has been uniformly the same, particularly in light of the fact that a continuous automaticallycontrolled procedure was employed. ln thi's 'pr'ocedure the autoclave was a conventional autoclave made of stainless steel and having a capacity of approximtely 15 gallons anda working pressure of one thousand pounds gauge pressure. This pressure obviously 'is far beyond any-requirement as far as propylene oxide 5 goes "unless there is a reaction of explosive violence involved due to accident. The autoclave was equipped with the conventional devices and opehings'su'ch as the variable-speed stirrer operating at speeds from R. P. M. to '500 R. l M.; thermometer well and thermocouple for mechanical thermometer; emptying outlet; pressure gauge, manual vent line; charge hole for initial reactants; at least one connection for introducingthe alkylene oxide, such as propylene oxide or ethylene oxide, to the bottom of the autoclave; along with suitable devices for both cooling and heating the autoclave, such as a cooling jacket, and, 'preferably, coils in addition thereto, withthe jacket so arranged that it is suitable for heating with steam or cooling with water and further equipped with electrical heating devices. Such autoclaves are, of course, in essence small-scale replicas of the usual conventional autoclave used in oxyalkylation procedures. In some instances in exploratory preparations an autoclave having a smaller capacity, for instance, approximtely-3 liters in one case and about 1% gallons in another case, was used.

Continuous operation, or substantially continuous operation, was achieved by the use of a separate container to hold the alkylene oxide being employed, particularly propylene oxide. In conjunction with the smaller autoclaves, the container consists essentially of a laboratory bomb having a capacity of about one-half gallon, or somewhat in excess thereof. In some instances a larger bomb was used, to wit, one having a capacity of about one gallon. This bomb was equipped, also, with an inlet for charging, and an eductor tube going to the bottom of the container so as to permit discharging of alkylene oxide in the liquid phase to the 'autoclave. A-bomb having a capacity of about pounds was used in connection with the -gallon autoclave. Other conventional equipment consists, of course, of the rupture disc, pressure gauge, sight feed glass, thermometer connection for nitrogen for pressuring bomb, etc. The bomb was placed on a scale during use. The connections between the bomb and the autoclave were flexible stainless steel hose or tubing so that continuous weighings could be made without breaking or making any connections. This applies also to the nitrogen line, which was used to pressure the bomb reservoir. To the extent that it was required, any other usual conventional procedure or addition which provided greater safety was used, of course, such as safety glass protective screens, etc.

Attention is directed again to what has been said previously in regard to automatic controls which shut off the propylene oxide in event temperature of reaction passes out of the predetermined range or if pressure in the autoclave passes out of predetermined range.

With this particular arrangement practically all oxypropylations become uniform in that the reaction temperature was held within a few degrees of any selected point, for instance, if 105 C. was selected as the operating temperature the maximum point would be at the most 110 C. or 112 C., and the lower point would be 95 or possibly 98 C. Similarly, the pressure was held at approximately 30 pounds maximum, within a 5-pound variation one way or the other, but might drop to practically zero, especially where no solvent such as xylene is employed. The speed of reaction was comparatively slow under such conditions as compared with oxyalkylations at 200 C.

Numerous reactions were conducted in which the time varied for a complete oxypropylation, including several steps, from one day up to two days for the completion of the final member of the series. In some instances the reaction took place in considerably less time, for instance, 24 hours or less, as illustrated by subsequent examples. In the case of partial oxypropylation or step-wise oxypropylation I have found that the periods from 2 to 8 hours were convenient. In the following examples the time period varied from approximately 4 hours to 6 hours. The minimum time recorded, as a matter of fact, was 4 hours. Reactions indicated as being complete in 6 hours may have been complete in a lesser period of time in light of the automatic equipment employed. This applies also where reactions were conducted in a shorter period of time as, for example, in t hours. In the addition of propylene oxide, in the autoclave equipment as far as possible the valves were set so all the propylene oxide if fed continuously would be added at a rate so that the predetermined amount would react within the first 15 hours of the 24-hour period or two-thirds of any shorter period. This meant that if the reaction was interrupted automatically for a period of time for pressure to drop or temperature to drop the predetermined amount of oxide would still be added in most instances well within the predetermined time period. Sometimes where the addition was a comparatively small amount in a 10-hour period there would be an unquestionable speeding up of the reaction, by simply repeating the examples and using 3, 4 or 5 hours instead of 10 hours.

When operating at a comparatively high temperature, for instance, between 150 to 200 C.,

an unreacted alkylene oxide such as propylene oxide, makes its presence felt in the increase in pressure or the consistency of a higher pressure. However, at a low enough temperature it may happen that the propylene oxide goes in as a liquid. If so, and if it remains unreacted there is, of course, an inherent danger and appropriate steps must be taken to safeguard against this possibility; if need be a sample must be withdrawn and examined for unreacted propylene oxide. One obvious procedure, of course, is to oxypropylate at a modestly higher temperature, for instance, at to C. Unreacted oxide affects determination of the acetyl or hydroxyl value of the hydroxylated compound obtalned.

The higher the molecular weight of the compound, i. e., towards the latter stages of reaction, the longer the time required to add a given amount of oxide. One possible explanation is that the molecule, being larger, the opportunity for random reaction is decreased. Inversely, the lower the molecular weight the faster the reaction takes place. For this reason, sometimes at least, increasing the concentration of the catalyst does not appreciably speed up the reaction, particularly when the product subjected to oxyalkylation has a comparatively high molecular weight. However, as has been pointed out previously, operating at a low pressure and a low temperature even in large scale operations as much as a week or ten days time may lapse to obtain some of the higher molecular weight derivatives from monohydric or dihydric materials.

In a number of operations the counterbalance scale or dial scale holding the propylene oxide bomb was so set that when the predetermined amount of propylene oxide had passed into the reaction the scale movement through a time operating device was set for either one to two hours so that reaction continued for 1 to 3 hours after the final addition of the last propylene oxide and thereafter the operation was shut down. This particular device is particularly suitable for use on larger equipment than labora tory size autoclaves, to wit, on semi-pilot plant or pilot plant size, as Well as on large scale size. This final stirring period is intended to avoid the presence of unreacted oxide.

In this sort of operation, of course, the temperature range was controlled automatically by either use of cooling water, steam, or electrical heat, so as to raise or lower the temperature. The pressuring of the propylene oxide into the reaction vessel was also automatic insofar that the feed stream was set for a slow continuous run which was shut off in case the pressure passed a predetermined point as previously set out. All the points of design, construction, etc, were conventional including the gauges, check valves and entire equipment. As far as I am aware at least two firms, and possibly three, specialize in autoclave equipment such as I have employed in the laboratory, and are prepared to furnish equipment of this same kind. Similarly pilot plant equipment is available. This point is simply made as a precaution in the direction of safety. 'Oxyalkylations, particularly involving ethylene oxide, glycide, propylene oxide, etc., should not be conducted except in equipment specifically designed for the purpose.

Example 1a' The reaction vessel employed was a stainless about 115 quired to add this oxide was 4 /2 hours.

subjected to further oxyprop in Example 30., immediately following.

steel autoclave with the usual devicesfor heat ing heat control, stirrer, inlet, outlet, etc., which are conventional in'this type o'f apparatus. The capacity or the autoclave was approximately liters. 'This'was purely a-matter ofconvenience in light of thesize of the particular batch 'being processed. In other instances a l5-gallon autoclave was employed for comparably larger batches. The construction-and operation-of both size 'autoclaves was substantially the same. In both-instances the stirrer operated at approxiniately 300 to 350 R. P. M. There were charged into the autoclave 260 grams of hexanetrioll-,2',6, along with grams of sodium methylate. No solvent was employed. Sodium methylate was used although ground caustic soda or ground caustic potash is equally satisfactory.

The autoclave'was sealed, swept with nitrogen gas, a'ndstirring started immediately, and heat applied. The temperature was allowed to'rise to slightly'above the boiling point of'w-ater, to wit, C. At this point the addition of propylene oxide was started. It Was added at such speed that it was absorbed by the reaction as rapidly asadded. During the temperature was held at120 l25 C. In this particular step, and in all succeeding steps, the

this oxypropylation step, and in all succeeding oxypropylation steps,

propylene oxide, and 11.3 grams of sodium methylate, were subjected to further oxypropylation in the manner employed in Examples 1a and 2a, preceding. The conditions of temperature and pressure were the same as in the previous examples. The amount of oxide added was 1035 grams, which was added in a 6-hour period, and at 'a fairly constant rate. When the oxypropylation was complete, part of the reaction mass was withdrawn and the remainder subjected to further oxypropylation as described in Example 4a, immediately following.

Example 4a 1568 grams of the reaction mass identified as Example 3a, preceding, and equivalent to 60.5 grams of the triol, 1501.7 grams of propylene oxide and 5.8 grams of sodium methylate, were subjected to further oxypropylation in the manner described in previous examples. The amount of oxide added was 706 grams. The time required for the addition was 6 hours. The oxide was added at a fairly constant rate.

What has been said preceding is presented in tabular form in Table 1, following, with some added information as to molecular weight and as to solubility of the reaction products in water, xylene, and kerosene.

TABLE 1 Composition before Composition at end Max Max. T

1 pres. ime n. o Oxide Cata- Theo H. o. Oxide Catal-Iyd. W 6 lbs. 5d his. 211112., amt, lyst, M amt, amt, lyst, mol. in.

lbs. lbs. lbs. lbs. lbs. lbs. wt.

was withdrawn and the remainder subjected to further oxypropylation as described in Example 2a, immediately following.

Example-2a 1750 grams of the reaction mass previously identified as Example la, and equivalent to 169.5 grams of hexanetriol-l,2 ',6, 1564.;2 grams of propylene oxide, and 16.3 grams 'of sodium methylate, were subjected to further oxypropylation'under substantially the same conditions as described in'Example 1a, preceding. 1160 grams of propylene oxide were added. The time re- The oxide was added at'a fairly constant rate. As previously stated, the

la, preceding. When the reaction was complete, part of the reaction mass was withdrawn and ylation as described Example 30.

2019 grams of the reaction mixture previously identified as Example 20., preceding, and equivaletto 117.3 grams of the trio], 1890.4 grams of conditions of oxypropylation were substantially the same as in Example "Example 1a was emulsifiable in water, soluble in xylene and insoluble in kerosene; Example 20. was 'emulsifiable in water, soluble in both xylene and'kerosene; Example 3a was emulsifiable-toinsoluble in water, and soluble in both xylene and kerosene; and Example 40. was insoluble in water, and soluble inboth xylene and kerosene.

The products obtained were usually viscous, somewhat syrupy liquids of amber, dark amber, or reddish color. The color may be due to a trace of iron because of contamination from the vessel employed. However, even when stainless steel is employed of such character that contamination by iron seems out of the questiomthere is still discoloration, probably due to the inherent nature of the initial raw material or a subsequent carmelization-like reaction. If it had been desirable, any suitable solvent might have been present during oxyalkylation, so long as it was inert to propylene oxide. Xylene is an example of such a solvent.

The derivatives 50 obtained can be decolorized in the usual manner by treating with charcoal, filtering clay, or the like. However, for the bulk of purposes for which such materials are used there is no necessity for decolorizing and in many instances, as in the present instance, the solvent may remain in the material.

It is obvious that certain modifications can be made which'do not depart from the spirit of the invention. Modifications of hexanetriol-1,2,6 which bear a simple genetic relationship to that 'material and are water-soluble may be used as starting materials, provided the products obtained from them satisfy the specifications for such products, set out herein in detail. For example, the hexanetriol-l,2,6 could be treated with a mole or two or thereabouts or ethylene oxide or glycide, and the product employed as a starting material.

Similarly, after oxypropylation starts one could interrupt the procedure and introduce a mole or two of ethylene oxide, or glycide, and then resume oxypropylation. Either one or" such minor modifications would not significantly, nor perhaps even detectibly, change the character of the initial raw material or the final oxypropylation derivative. Needless to such variation would not be departing the slightest from the spirit of the invention.

If one examines the preceding table, it will be seen that if one starts with hexanetriol-l,2,6, of molecular weight 134, and adds successive amounts of propylene oxide, one obtains products having steadil declining proportions of this starting material, from about 10% down to less than 3%. As one approaches the maximum molecular weight of the presently included products, i. e., 10,000, the initial material may contribute little more than 1% to the final product. The maximum contribution, from the table, is somewhat less than 10% of the final oxypropylated triol.

Speaking of insolubility in water or solubility in kerosene such solubility test can be made simply by shaking small amounts of the materials in a test tube with water, for instance, using 1% to 5% approximately based on the amount of water present.

Needless to say, there is no complete conversion of propylene oxide into the desired hydroxylated compounds. This is indicated by the fact that the theoretical molecular weight based on a statistical average is greater than the molecular weight calculated by usual methods on basis of acetyl or hydroxyl value. Actually, there is no completely satisfactory method for determining molecular weights of these types of compounds with a high degree of accuracy when the molecular weights exceed 2,000. In some instances the acetyl value or hydroxyl value serves as satisfactorily as an index to the molecular weight as any other procedure, subject to the above limitations, and especially in the higher molecular weight range. If any difliculty is encountered in the manufacture of the esters as described in Part 2 the stoichiometrical amount of acid or acid compound should be taken which corresponds to the indicated acetyl or hydroxyl value. This matter has been discussed in the literature and is a matter of common knowledge and requires no further elaboration. In fact, it is illustrated by some of the examples appearing in the patent previously mentioned.

PART 2 As previously pointed out the present invention is concerned with acidic esters obtained from the oxypropylated derivatives described in Part 1, immediately preceding, and polycarboxy acids, particularly tricarboxy acids like citric, and dicarboxy acids such as adipic acid, phthalic acid, or anhydride, succinic acid, diglycollic acid, sebacic acid, azelaic acid, aconitic acid, maleic acid or anhydride, citraconic acid or anhydride, maleic acid or anhydride adducts as obtained by the Diels-Alder reaction from products such as maleic anhydride, and cyclopentadiene. Such acids should be heat stable so they are not decomposed during esterification. They may contain as many as 36 carbon atoms as, for example, the acids obtained by dimerization of unsaturated iatty acids, unsaturated monocarboxy fatty acids, or unsaturated monocarboxy acids having 18 carbon atoms. Reference to the acid in the hereto appended claims obviously includes the anhydrides or any other obvious equivalents. My preference, however, is to use polycarboxy acids having not over 8 carbon atoms.

The production of esters including acid esters (fractional esters) from polycarboxy acids and glycols or other hydroxylated compounds is well known. Needless to say, various compounds may be used such as the low molal ester, the anhydride, the acyl chloride, etc. However, for purpose of economy it is customary to use either the acid or the anhydride. A conventional procedure is employed. On a laboratory scale one can employ a resin pot of the kind described in U. S. Patent No. 2,499,370, dated March 7, 1950 to De Groote and Keiser, and particularly with one more opening to permit the use of a porous spreader if hydrochloric acid gas is to be used as a catalyst. Such device or absorption spreader consists of minute Alundum thimbles which are connected to a glass tube. One can add a sulfonic acid such as paratoluene sulfonic acid as a catalyst. There is some objection to this because in some instances there is some evidence that this acid catalyst tends to decompose or rearrange the oxypropylated compounds, and is particularly likely to do so if the esterification temperature is too high. In the case of polycarboxy acids such as diglycollic acid, which is strongly acidic there is no need to add any catalyst. The use of hydrochloric gas has one advantage over paratoluene sulfonic acid and that is that at the end of the reaction it can be removed by flushing out with nitrogen, whereas there is no reasonably convenient means available of removing the paratoluene sulfonic acid or other sulfonic acid employed. If hydrochloric acid is employed one need only pass the gas through at an exceedingly slow rate so as to keep the reaction mass acidic. Only a trace of acid need be present. I have employed hydrochloric acid gas or the aqueous acid itself to eliminate the initial basic material. My preference, however, is to use no catalyst whatsoever.

The products obtained in Part 1 preceding may contain a basic catalyst. As a general procedure I have'added an amount of half-concentrated hydrochloric acid considerably in excess of what is required to neutralize the residual catalyst.

The mixture is shaken thoroughly and allowed to stand overnight. It is then filtered and refiuxed with xylene present until the water can be separated in a phase-separating trap. As soon as the product is substantially free from water the distillation stops. This preliminary step can be carried out in the flask to be used for esterification. If there is any further deposition of sodium chloride during the reflux stage needless to say a second filtration may be required. In any event the neutral or slightly acidic solution of the oxypropylated derivatives described in Part 1 and is then diluted further with sufficient solvent of a suitable nature, so that one has obtained a solution containing about 4O% i5% oxypropylated triol. To this solution there is added a polycarboxylated reactant as previously described, such as phthalic anhydride, succinic acid or anhydride, diglycollic acid, etc. The mixture is refluxed until esterification is comas indicated by elimination of water or c op in carboxyl value. Needless to; say, if one produces a half-ester from an anhydride such as rithalic anhydride, no water is eliminated. I owever, if it is obtained from diglycollic acid, for example, water is.eliminatedi All such procedures were conventional and have" been so thoroughly described in the literature that further consideration will be. limited to a fewexamples and a comprehensive table.

Other procedures for eliminating'the residual basic catalyst, if any, may be. employed. For example, if the oxyalkylation is conducted in absence of a solvent, as in the foregoing examples, or the solvent is removed after oxypropylation, the oxypropylation end-productcan then be acidified with enough concentrated hydrochloric acid to just neutralize the residual basic catalyst. To this product one can then add a small amount, of anhydrous sodium sulfate (sufficient in quantity to take up any water that is present) and then subject the mass to. centrifugal force so as to eliminate the. hydrated sodium sulfate and probably the sodium chloride formed. The clear, somewhat viscous, straw-colored or amber liquid so obtained may contain asmall amount of sodium sulfate or sodium chloride. but, in any event, is perfectly acceptable for esterification in the manner described.

It is to bepointed out that the final products herein described are not polyesters in the sense that there is a plurality of. both oxypropylated compound radicals and acid radicals. The product here is characterized by having only one oxypropylated compound radical.

By following slight modifications of what has been said previously one-can conduct the esterification on a laboratory scale withv greater convenience. Obviously, if one startswith a polyhydric compound having 3 hydroxyls and adds a polycarboxy acid there is at least some opportunity for cross-linlsing'andformation of insoluble materials. However, insolubility or a gelaition efiect can arise in other ways, for instance, possible incipient cross-linking rather than intermediate or complete cross-linking, and also 12 to saynothing of peculiarities of structure. After the Water is removed in the case of the esterification by means of a water-insoluble solvent, such as benzene, xylene or the use of some other comparable solvent or mixtures, one is confronted with the fact that the acidic ester'is not necessarily soluble in such nonpolar solvent, and possibly because it either does cross-link or at least gives a. pseudo gel. I have used the terminology pseudo gel for the reason that suchgel is reversible as distinguished from a true nonreversible gel produced by cross-linking. The exact nature of this tendency to become insolu- 15 ble. or tendency toward gelation is obscure and not fully understood. In light of the effect of semi-polar solvents there may be. some relationship, and in fact an important one to hydrogen bonding factors.

However, by selection of solvent, one tends to eliminate this effect. In the present examples, I have found it desirable to employ xylene as the solvent present during the esterification procedure. After completion of such esterification g5 procedure and elimination of the water of reaction by distillation in the presence of such xylene solvent I usually prefer to add' to the xylene solution of the finished ester product a minor proportion of methanol. The amount of methanol added is usually 5%, 6%, or 7% of the nonhydroxylated solvents previously present. In Table 3, column 2, below, the solvent is recited as xylene-methanol. This reference is to products prepared as just stated, 1. e., xylene is the solvent present during the esterification step and methanol is the solvent added subsequently in preparing the final solution of the esters. All solutions of the oxypropylated triol, as before stated, were about 4.0%-45% concen- 40 trated, i. e., contained 55%-60.% of such solvent.

Any other desirable concentrations might have been equally well. employed. The finished esters of theexamples in the tables below are in the form of approximately 50% solutions in the 45 xylene-methanol solvent.

The data included in Tables 2 and 3 below, are

the fact that there are certain l1m1tat1ons as self-explanato y and V ry comp No further far as solubility goes in any large molecule, r l n 1 n c ry.

TABLE 2 Th Th t A t of Ex. e0. e0. W m Ex. No. Actual ol of acid ig' b? gfzfi hydrox. 23 :3 Polycarboxy reactant @5103 cmpd. H. o H. 0. Value tual (grs.) reactant la 1, 370 123 141 1, 194 95. 5 Di glycolic'acid 32, 2 la 1, 370 123 141 l, 194 95. 5 Oxalic acid 2 la 1, 370 123 141 1,194 95. 5 Aconitic acid 41 8 la 1, 370 123 141 1,194 95. 5 Adipic acid. 35. 0 1a 1, 370 123 141 l, 194 95. 5 Phtlialic anhydride. 35. 6 la .1, 370 123 141 l, 194 95. 5 Maleic anhydride. 23. 7 2a 2, 290 73. 5 97. 5 1, 725 103. 5 24 1 2a 2, 290 73. 5 97. 5 1, 725 103. 5 22 7 2a 2, 290 73. 5 97. 5 1, 725 103. 5' 31 3 2a 2,290 73. 5. 97. 5 1, 725 103. 5 Adipic acid 26. 3 2a 2, 290 73. 5 97. 5 1, 725 103. 5 Phthalic anhydride- 20. 6 2a 2, 290 73. 5 97. 5' 1, 725 103.5 Maleic anhydride 17.7 311 3, 480 48. 4 69. 0 2, 436 97. 5 Diglycolic acid" 16. 1 3a 3, 480 48. 4 69. 0 2, 436 97. 5 Oxalic ac 15.1 311 3, 480 48. 4 69. 0 2, 436 97. 5 Aconitic acid. 20. 9 3a 3, 480 48. 4 69. 0 2, 436 97. 5 Adipic acid. l7. 5 3a 3, 480 48. 4 60. O 2, 436 97. 5 Phthalic anhydride- 17. 0 3a 3, 480 48. 4 69. 0 2, 436 97. 5 Malcic anhydride 10.2 5,010 33. 6 65. O 2, 583 129. 2 Diglycolic acid- 20.1 411 5, 010 33. 6 65. 0 2, 583 129. 2 Oxalic acid.-. 18. 9 4c 5, 010 33:6 65. 0 2, 583 129. 2 Aconitic acid 20. 1 4a 5, 010 33. 6 65. 0 2, 583 129. 2 Adipic acid- 21. 9 4a 5, 010 33. 6 65. 0 2, 583 129. 2 Phthalic an ydr 22. 2 4a 5, 010 33. 6 65. 0 2, 583 129. 2 Maleic anhydride... 14. 7

TABLE 3 Time of esterification (hrs.)

Amt. solvent (e e) Solvent Xylene-methanol. dc

The procedure for manufacturing the esters has been illustrated by the preceding examples. If for any reason reaction does not take place in an acceptable manner, attention should be directed to the following details: (a) Recheck the hydroxyl or acetyl value of the oxypropylated triol and use a stoichiometrically equivalent amount of acid; (b) if the reaction does not pro-- ceed with reasonable speed, either raise the temperature indicated or else extend the period of time up to 12 or 16 hours if need be; (c) if necessary, use of paratoluene sulfonic acid or some other acid as a catalyst; (d) if the esterification does not produce a clear product a check should be made to see if an inorganic salt such as sodium chloride or sodium sulfate is not precipitating out. Such salt should be eliminated, at least for exploration experimentation, and can be removed by filtering. Everything else being equal, as the size of the molecule increases and the reactive hydroxyl radical represents a smaller fraction of the entire molecule, more difficulty is involved in obtaining complete esterification.

Even under the most carefully controlled conditions of oxypropylation involving comparatively low temperatures and long time of reaction there are formed certain compounds whose compositions are still obscure. Such side reaction products can contribute a substantial proportion of the final cogeneric reaction mixture. Various suggestions have been made as to the nature of these compounds, such as being cyclic polymers of propylene oxide, dehydration products with the appearance of a vinyl radical, or isomers of propylene oxide or derivatives thereof, i. e., of an aldehyde, ketone, or allyl alcohol. In some instances an attempt to react the stoichiometric amount of a polycarboxy acid with the oxypropylated derivative results in an excess of the carboxylated reactant for the reason that ap parently under conditions of reaction less reactive hydroxyl radicals are present than indicated by the hydroxyl value. Under such circumstances there is simply a residue of the carboxylic reactant which can be removed by filtration or, if desired, the esterification procedure can be repeated using an appropriately reduced ratio of carboxylic reactant.

Even the determination of the hydroxyl value and conventional procedure leaves much to be desired due either to the cogeneric materials previously referred to, or for that matter, the

14 presence of any inorganic salts or propylene oxide. Obviously this oxide should be eliminated.

The solvent employed, if any, can be removed from the finished ester by distillation, particularly vacuum distillation. The esters prepared as described above vary in color from yellow through amber, dark amber, to reddish-brown. Their viscosity varies somewhat but all of them may be termed rather syrupy viscous liquids. They show moderate viscosity, or sometimes increased viscosity in light of what has been said previously in regard to cross-linking, gelation, etc. Unless there is some reason to do otherwise, my preference is to handle these esters as 50% solutions in suitable sol-vents. They can be bleached with bleaching clays, filtering chars, and the like. However, for the purpose of demulsification or the like, color is not a factor and decolorization is not justified.

Having thus described my invention, what I claim as new and desire to secure by Letters Patent, is:

l. A monomeric acidic fractional ester of the following structure:

in which R is the radical of hexanetriol-l, 2, 6, and R is the radical of a polycarboxy acid selected from the group consisting of acyclic and isocyclic polycarboxy acids having not more than 8 carbon atoms and composed of carbon, hydrogen and oxygen of the formula:

COOH

(COOHM in which n represents the whole numbers 1 to 2, and n represents a whole number varying from 6 to 30; with the proviso that n be the statistical average based on the amount of propylene oxide reacted with the initial triol R(OH)3; said triol being free from any radical having at least 8 uninterrupted carbon atoms; and with the further proviso that the statistical average molecular weight of said oxypropylated triols be within the range of 1,000 to 10,000.

2. A monomeric acidic fractional ester of the following structure:

o oaH5o),.ooR' oooH),.' RO(C3HO),.OOR(COOH),.I

O(CSH6O)HOCR'(COOH)1|' in which R is the radical of hexanetriol-l, 2, 6, and R is the radical of a polycarboxy acid selected from the group consisting of acyclic and isocyclic polycarboxy acids having not more than 8 carbon atoms and composed of carbon, hydrogen and oxygen of the formula:

OOOH

in which n represents the whole numbers 1 to 2, and n represents a whole number varying from 6 to 30; with the proviso that n be the statistical average based on the amount of propylene oxide reacted with the initial triol R(OH)3; said triol being free from any radical having at least 8 uninterrupted carbon atoms; and with the further proviso that the statistical average molecular Weight of said oxypropylated triols be within the range of 1,000 to 10,000; and that the preceding 15 provisos;arefbased;on completereactiondnvolying the; propylene oxideandgthe hexametriol-.1v, 2, 6 andw-ith theproviso that there-be-onemole of; the polycarboxy acid for each available hydroxyl radical.

3. A- monomeric acidic fractional ester of the following structure:

o(c-3Hto),.ooR'(oo0H) afowanzmflooa'woon) O(CaHnO),.OCR(COQH) in which R is the radical oi,hexanetriol-l, 2, 6, and; R- is the radical or a dicarboxy acid selected from the group; consisting of acyclic and isocyclic dicarboxy acidshaving not more than 8 carbon atoms, and composed of carbon, hydroen and. oxy en of thejormula:

COO'H- COQH- and n represents a whole number varyingirom 6'to 30; with the-proviso that n be: the statistical average based on the amount of propylene oxide reacted with the initial triol R(OI-I)3; said triol being free from any radicalhaving at least 8 uninterrupted carbon atoms; and with the further proviso that the statistical average molecular weight of said oxypropylated triols be within the range of 1,000 to 10,000, and that the preceding provisos are based on completereaction involving the propylene oxide and the hexanetriol-l, 2, 6, and with the proviso that there be one mole of the dicarboxy acid for each available hydroxyl radical. 1

4. A monomeric acidic fractional ester of the following structure:

O(C3HuO),.OCR'(COOH) R-O (CaH'uO'),.O oR'(co-o11 (CaHoO MOCRKCOOH) 1-6 in which R is the radical of hexanetri01-1,2,6, andB' is, the radical ofa dicarboxy acid selected from the group consisting of acyclic and isocyclic dicarboxy acids having not more than 8 carbon atoms and composed of carbon, hydrogen and oxygen of theformll a and nrepresents a whole number varying from 6'00 30 ;;with the proviso that n be the statistical, average based on the amount of propylene oxide reacted with the initial; triol R(OH')3; said triol being free from any radical having at least 8 uninterrupted carbon atoms; and with the further proviso that the statistical average molecu larweight of said qxypropylated triols be within the range of 1,000 to 10,000, and that the preceding; provisos ar based on complete reaction involving th propylene oxide and the hexanetriol- 1,2 6, and with the proviso that there be one mole of the dicarboxy acid for each available. hydr xylradical, and that the ica b xy acid. have. not, more than 8; carbon. at m 5, The product of claim 4 wherein the dicarboxy acidis phthalicacid.

6. The product of claim 4 wherein the dicarboxy acid is maleic acidv '7. The product of claim 4 wherein th dicarboxy acidis succinic acid.

8. The product of claim 4 wherein the. dicarboxy acid is citraconic acid.

9. The product of claim 4 wherein the dicarboxy acid isdiglycolicacid,

DE GBQQ' ZE,

No referencesicited. 

1. A MONOMERIC ACIDIC FRACTIONAL ESTER OF THE FOLLOWING STRUCTURE: 